Download Life-Cycle Assessment Tools for Building Analysis

The Pennsylvania Housing Research Center
Life-Cycle Assessment Tools for Building Analysis
Research Brief: RB0511
Guiyuan Han, M.Sc. and Jelena Srebric, Ph.D.
INTRODUCTION
A Life-Cycle Analysis (LCA) is a methodology to
assess the total costs and environmental impacts of a
product. LCA is especially useful when it comes to
evaluating trade-offs between initial and operating
costs. This builder brief will introduce four different
LCA tools, and discuss the similarities and
differences among these tools when applied to LCA
of buildings.
Building Energy Consumption
Energy consumed by buildings represents a
significant fraction of the total energy use in the
world. In developed countries, energy consumption
from buildings comprises 20% to 40% of the total
energy use, and this percentage is higher than either
industrial or transportation energy consumption in
both European Union and United States. [1].
Therefore, building energy cost analyses is an
important consideration. These analyses should be
performed in early building design stages.
In a standard building design approach, building
energy costs are typically estimated by load
calculation and annual energy analysis software,
such as DOE-2 [2] and EnergyPlus [3]. These
methods are appropriate to analyze the building
thermal loads and size the cooling or heating
equipment. A building and building systems will
consume a large amount of energy and money
during their lifespan. The energy consumption
during the entire lifespan should be considered when
evaluating different building design solutions.
Building operation and maintenance practices can
play a significant role in this evaluation.
Life-Cycle Assessment (LCA)
Life-Cycle Assessment (LCA) is an effective way to
help make informed investment decisions during the
early building design stages. LCA is an analytical
methodology for a systematic evaluation of the
environmental impacts of a product or service
system through all stages of its life cycle [4]. LCA
evaluations include potential environmental impacts
from raw material acquisition to production, use, and
disposal. It takes into account all costs of
constructing, owning, and disposing of a building or
building system. LCA evaluations have been used in
many industries and fields of research, and it is
helpful to assess building products and assemblies in
an integrated design process.
LCA evaluations for buildings can inform decisions
regarding selection of different building systems.
For example, improvements of building enclosure
system will take additional capital investments, but
will also bring significant net energy savings during
the building lifespan. Without LCA, a decision
maker is likely to ignore the benefit of these
improvements and only focus on the initial costs.
Moreover, LCA is especially useful when project
alternatives that perform the same function, but
differ with respect to the initial costs and operating
costs, are to be compared in order to select the one
that maximizes net savings. For example, LCA will
help determine whether the incorporation of a highperformance HVAC or glazing system, which
increases the initial costs, but results in greatly
reduced operating and maintenance costs, is costeffective or not. A lowest Life-Cycle Cost (LCC) is
the most straightforward and an easy-to-interpret
measure for economic performance.
LIFE-CYCLE ASSESSMENT TOOLS FOR
BUILDINGS
A large number of life-cycle assessment tools are
developed for designers and researchers to analyze
the life-cycle cost of buildings. LCA tools for
buildings measure the economic costs and
environmental performance of building products and
systems by using the life-cycle assessment approach
specified in the ISO 14040 series of standards. The
life-cycle stages of buildings include raw materials,
manufacturing, transportation, use, and end of life.
The following four tools are reviewed:
1. BEES
2. ATHENA EcoCalculator
3. ATHENA Impact Estimator
4. SimaPro
BEES: A Product-Level LCA Tool
The Building for Environmental and Economic
Sustainability (BEES) software was developed by
the U.S. Environmental Protection Agency (EPA)
Engineering Laboratory. It is a useful methodology
for selecting cost-effective, environmentallypreferable building products. It is available online
via the BEES Online access to designers, builders,
and product manufacturers. BEES Online includes
actual environmental and economic performance
data for two-hundred and thirty building products,
which is sufficient for most of the analysis.
All stages in the life of a product are analyzed: raw
material acquisition, manufacture, transportation,
installation, use, as well as recycling and waste
management. Economic performance is measured
using the ASTM standard life-cycle cost method,
which covers the costs of initial investment,
replacement, operation, maintenance and repair, and
disposal. Environmental impacts of building
products are analyzed using TRACI (Tool for the
Reduction and Assessment of Chemical and other
environmental Impacts). Environmental and
economic performance data are combined into an
overall performance measure using the ASTM
standard for Multi-Attribute Decision Analysis.
To select environmentally-preferred, cost-effective
building products, users need to follow three main
steps:
1. Set the parameters
Weighting factors are an important input in BEES,
used to combine different elements into a uniform
scale of evaluation. Environmental impact weights
are factors used to combine different environmental
impacts in an evaluation. In the section on model
setting of BEES, users can choose environmental
impact category weights from three pre-defined
weight-setting categories or define weights by
selecting the user-defined weight set. Similarly,
another weighting factor, performance weight, is
introduced to integrate environmental performance
and economic performance in BEES.
2. Select alternative building products
Information on different building products is built in
the program, so that users can choose the products
from the existing database. Two-hundred and thirty
products are divided into seven major group
elements.
3. View the BEES Online results
BEES Online produces graphs showing product
scores. The larger the score, the worse the
performance is for the selected building products.
ATHENA EcoCalculator: An Assembly-Level
LCA Tool
The ATHENA EcoCalculator for assemblies
includes a series of spreadsheets developed by the
Athena Institute in association with the University of
Minnesota and Morrison Hershfield Consulting
Engineers. The tool provides instant LCA results for
commonly used building structure and envelope
assemblies. It is available free of charge with two
versions: EcoCalculator for Commercial Assemblies
and the new EcoCalculator for Residential
Assemblies. The program covers information on
hundreds of common building assemblies.
This calculator estimates the environmental effects
of building materials and their related processes. It
does not estimate or account for operational energy.
It is intended to be used to quantitatively compare
different types of building materials and assemblies.
This calculator accounts only for environmental
impacts, such as global warming potential,
acidification potential, ozone depletion potential,
HH respiratory effects potential, eutrophication
potential, and smog potential, and do not include
associated economic costs. To use EcoCalculator,
following three main steps are needed:
1. Select and download the appropriate spreadsheet
of EcoCalculator
For an economic analysis, ATHENA IE can provide
users with a report of material costs, listing the
quantity of all the materials required in the building.
The results of ATHENA IE focus on environmental
impact of different buildings. In contrast to
EcoCalculator analyses, an analysis undertaken by
Impact Estimator includes the environmental effects
from both building construction and operation.
Users have to download a suitable spreadsheet
version by selecting the most appropriate climatic
zone and the building height. These choices will
affect the assembly definitions and characteristics.
To analyze building performance, users need to
perform the following three main steps:
2. Input relevant parameters
In this step, users need to define gross floor area and
building life expectancy in the project, as well as
select project location and building type.
There are several assemblies covered in the each
version of spreadsheets. After downloading a
spreadsheet, user needs to select the assembly sheet
from one of the categories: Exterior walls, Roofs,
Intermediate floors, Interior walls, Windows,
Columns and beams. The environmental impacts for
each assembly have been built in the spreadsheets.
Users only need to input the areas of assemblies into
the yellow highlighted cells.
3. View the results
After step 2, the results will be automatically
displayed in the blue highlighted cells. This tool
determines the extended environmental effects of the
materials used in a building based on eight impact
categories. The summary of all assemblies’
environmental impacts will show in the summary
sheet.
ATHENA Impact Estimator (IE): A WholeBuilding Level LCA Tool
In North America, the ATHENA Impact Estimator
for Buildings, also developed by Athena Institute, is
the only software that is particularly designed to
evaluate whole buildings based on life-cycle
assessment methodology. Using IE, architects,
engineers, and others can assess and compare the
environmental impacts of industrial, institutional,
commercial and residential buildings. A trial version
is available online for a short period use. The
software is capable of modeling well over 1,000
structural and envelope assembly combinations.
1. Start a new project
2. Build a model in the project
Users can define building enclosure by selecting and
adding various assemblies into the model. Each
assembly can be modified by identifying relevant
parameters. This is helpful in defining a more
detailed model of a building according to the
analysis requirements.
3. Report the results
IE can show a general report for the selected project
with all the details of building performances.
Furthermore, two or more projects can be compared
in same graphs.
SimaPro: A Material-Level LCA Tool
SimaPro is a detailed LCA tool developed by PRé
Consultants, which contains a number of impact
assessment methods. SimaPro comes with a large set
of data libraries coving 6,000 processes. The
software covers all the details of life-cycle analyses.
The software can be used to design analysis models
in different fields of engineering. However, it takes
much a more significant time investment for the
users to learn to use the software. There are also
tutorial lessons offered by PRé Consultants.
The steps of application can typically be divided into
three parts: building model, assessment method
selection, and result overview according to project
requirements. Building a model in SimaPro is a
tedious process because many details have to be set
up. The software is relatively expensive, and it has
specific computer memory requirements due to
relatively complex computations.
CASE STUDIES
In order to compare performance of the reviewed
LCA tools, this section presents several case studies.
A few examples are also provided to directly
compare the analysis results using different tools.
BEES
Using BEES, the performance of two or more
products can be directly compared in one study. For
example, the performance of an OSB-sheathed wall
and plywood-sheathed wall are compared. Table 1
shows the main parameters assumed for this case
study.
Table 1: Parameters in the case study
Parameters
Area (ft2)
Building Life (yr)
Transportation Distance
(miles)
Environmental Impact
Weights
Values
1
50
500
Equal Weights
Figure 1: Economic performance
Figure 3: Comparison of the overall performance
Figures 1 through 3 show economic costs and
environmental impacts with a lower score indicating
lower cost or impact. In Figure 1, the percentage in
the legend is the discount rate excluding inflation. In
Figure 2, the percentages shown in the legend are
environmental impact category weights. In Figure 3,
performance weights are shown as the percentages in
the legend. Per the discussion on BEES: a productlevel LCA tool, all of these numbers could be set at
the beginning of analysis.
In this case study, the economic performance of
OSB Wall is better than Plywood Wall, which is
shown in Figure 1. However, building owners might
not care only about the economic analysis. Further
BEES analyses indicate that the overall
environmental performance of Plywood Wall is
much better during the 50-year life cycle because of
its lower environmental impacts as shown in Figures
2 and 3. In the environmental performance report,
BEES gives a much more detailed breakdown of
results than other LCA tools. For example, regarding
global warming impact, there are CO2 equivalencies
for every greenhouse gas listed in the BEES result.
Other programs only provide the overall CO2
equivalent.
ATHENA Impact Estimator (IE)
ATHENA Impact Estimator (IE) is another good
tool to compare two projects. In contrast to BEES,
IE focuses on the analyses of a whole building rather
than just materials themselves. To illustrate this, the
authors created a model of a whole building with
two different external wall types, OSB and Plywood,
as shown in Table2.
Figure 2: Environmental performance
Table 2: Parameters in the case study
Parameters
Case Study1
Case Study2
Area (ft2)
48
Building Life (yr)
50
Foundation
Concrete: 4000psi
Thickness: 4 in
Fly ash: 25%
Modify Wood I Joist Roof
Decking thickness: 5/8in
Roof
Decking Type: OSB
Live Load: 50 psf
Wood-I Joist: ½” thick OSB webs, and 2.5”
x 1.5” LVL flanges
Walls
OSB Walls
Plywood Walls
Comparative Tool Analyses of Assemblies
The analysis based on EcoCalculator is the
assembly-level methodology. The details of entire
assemblies are built in the EcoCalculator spreadsheet
chosen by users. Once the building location and type
are decided, the components of the building
enclosure are also determined. In BEES, the
materials closest to typical building enclosure
products are selected in order to directly compare the
analysis results between BEES and EcoCalculator.
The details of products and analysis results are
shown in Tables 3 and 4. In Table 4, the results
calculated with BEES and EcoCalculator are
compared with a degree of interpretation in selecting
materials within these two LCA tools. Although
these two tools are built on the same database (U.S.
LCI), they emphasize different materials. The
characters of various components are selected and
integrated inside of these tools. Therefore, the global
warming potential results of wall assemblies are
similar, but not exactly the same.
Table 3: Parameters in the case studies
Parameters
Figure 4: Comparison of
potential by life-cycle stages
global
warming
Figure 4 presents IE results for the building with two
different wall types. Instead of listing only the
overall CO2 equivalent for each individual building
component, the global warming potential is
illustrated in terms of several stages of building lifecycle. In this example, the Plywood Wall is again
depicted as being more environmentally friendly,
especially in the manufacturing stage of the
lifecycle.
From the two examples evaluated in BEES and IE,
the same environmental impacts could be shown in
different ways. This may help users determine which
tool they prefer to use.
BEES
EcoCalculator
Area (ft2)
1
Building Life (yr)
50
Environmental
Impact
Weights between
different impact
Transportation
Distance (miles)
Global Warming Potential (GWP)
equal weight
0
Table 4: Comparative analysis of global
warming potential with BEES and EcoCalculator
BEES
Assembly
1
EcoCalculator
Materials
GWP
(gCO2/ft2)
Generic Vinyl
Cladding
1523
Generic
Plywood
Sheathing
377
Anonymous
R-19 Product
Generic
Gypsum Board
Generic Latex
Paint
240
1916
101
Materials
Generic Brick
& Mortar
3499
Generic
Plywood
Sheathing
377
Anonymous
R-19 Product
Generic
Gypsum Board
Generic Latex
Paint
240
1916
101
Latex Paint
3790
Brick
Cladding
Wood
Structural
Panel
Sheathing
R-19 Cavity
Insulation
Gypsum
Board
Assembly
3
1147
Generic
Plywood
Sheathing
377
Anonymous
R-19 Product
Generic
Gypsum Board
Generic Latex
Paint
240
1916
101
3781
LCA Tools
SimaPro
BEES
PRé Consultants EPA
Development
(Netherlands)
(US)
organization
Analysis level
Variable
Product
Program
high
low
complexity
Model flexibility
high
low
Detail coverage
high
low
Process
Y
N
contribution
analysis
Energy
Y
Y
consumption
Environmental
Y
Y
impact
Economic costs
Y
Y
Overall
Y
Y
performance
ATHENA
EcoCalculator
ATHENA
Impact
Estimator
ATHENA
(Canada)
Assembly
ATHENA
(Canada)
Building
low
medium
low
low
medium
medium
N
Y
N
N
Y
Y
N
Y
N
N
CONCLUSIONS
Latex Paint
6133
Generic
Stucco
GWP
(gCO2/ft2)
Vinyl
Cladding
Wood
Structural
Panel
Sheathing
R-19 Cavity
Insulation
Gypsum
Board
4157
Assembly
2
Table 5: The summary of properties for
reviewed LCA tools
5580
Stucco
Cladding
Wood
Structural
Panel
Sheathing
R-19 Cavity
Insulation
Gypsum
Board
Latex Paint
4630
DISCUSSION
The LCA tools that were reviewed were developed
by three different organizations, resulting in four
different tools, each with their own strengths and
weaknesses. Table 5 is a brief summary of important
properties for different LCA tools.
Life-cycle assessment is a comprehensive evaluation
of building performance over its entire lifespan.
There are many LCA tools developed for different
fields of application. This study covered four LCA
tools for building analyses, and discussed their
applications. This paper started from the discussion
of model constructions inside these tools, followed
by case studies to compare different tools based on
similar analysis conditions.
For the model construction, these four tools have
different levels of flexibility and detail. Although
SimaPro is the most complicated LCA tool reviewed
in this study, it has the flexibility required to deal
with complex building models. If a user wants to
work on details of every process, SimaPro will also
be the best choice. However, it will also take some
time to learn to build models in SimaPro. If the users
are interested in a more general analysis, they can
turn to BEES and Athena EcoCalculator, which will
significantly save time in the model set-up stage.
SimaPro, which has the most powerful calculation
engine, offers dozens of impact assessments to
evaluate the performance of different products.
In terms of performance, analysis of environmental
impacts is covered by all the tools in this study.
Users could select appropriate tools for particular
analysis required in their projects. Compared to
environmental
impacts
assessment,
energy
consumption analyses can be only performed by
SimaPro, BEES, and IE. To pursue an integrated
analysis of buildings, overall performance is
produced by BEES, which combines environmental
performance and economic performance into a
uniform scale of evaluation.
LCA is an analytical method to evaluate a product or
system through all stages of its life cycle. Given the
fact that different projects have various objectives of
analysis, builders, architects, and engineers, should
define the expected results and details of interest for
their projects before starting life-cycle analyses in
order to choose the right tool. Time and money
limitations could also be influential factors in the
selection of appropriate LCA tools.
REFERENCES
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3, pp. 394-398, 2008.
[2]. F. C. Winkelmann, B. E. Birdsall, W. F. Buhl,
K. L. Ellington, J. J. Hirsch, and S. Gates, DOE2 supplement: Version 2.1E. 1993.
[3]. D. B. Crawley, L. K. Lawrie, C. O. Pedersen,
and F. C. Winkelmann, “Energy plus: energy
simulation program.,” ASHRAE Journal, vol. 42,
no. 4, pp. 49-56, Apr. 2000.
[4]. ISO
International
Organization
for
Standardization,
“ISO
International
Organization for Standardization.”[Online].
Available:
http://www.iso.org/iso/catalogue_detail?csnumb
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